The normal and pathological role of metabolically dependent cell surface antigens (MDA) will be studied by a combination of immunological, chemical and cell culture methods. One of the objectives of this study is to learn about the relationship between MDA shared by cells of common embryological origin, that is, by primary ento-, meso- and ectodermal MDA and by the differentiated tissue specific MDA. A further objective aims at understanding the mechanisms of unmasking of the MDA and thus at an understanding of conditions which determine the sensitivity of organized tissue to antibodies and sensitized cells. Furthermore, the quantitative relationship between the number of metabolically dependent and independent cell surface antigens per cell in synchronized, virally-transformed and partially inhibited cultures will be investigated. One of the objectives of the investigation on the role of MDA in pathological processes will be the study of secondary participation of ocular MDA in systemic immunopathological diseases involving primarily tissues having a common embryological origin with the ocular tissues. Another objective is the study of the role of the normally masked MDA in autoimmunity. The animal experiments on the reactions of MDA and other cell surface antigens with anti-tissue antibodies which do not bind complement have as their objective, the study of the potential involvement of immunological mechanisms in disease states dominated by degenerative rather than inflammatory changes.